British scientist and theoretical physicist Stephen Hawking attends a launch event for a new award for science communication, called the Stephen Hawking Medal for Science Communication, in London, Britain Dec. 16, 2015. Photo: Reuters

British theoretical physicist Stephen Hawking, one of the world's most celebrated scientists, said the election of President-elect Donald Trump comes at "the most dangerous time for our planet."

Hawking linked Trump's election to the so-called Brexit referendum on leaving the European Union in Britain, calling it a sign that educated elites have far too long ignored working class voters. Hawking had urged Brits to remain in the European Union before the June refernedum.

"Whatever we might think about the decision by the British electorate to reject membership of the European Union and by the American public to embrace Donald Trump as their next president, there is no doubt in the minds of commentators that this was a cry of anger by people who felt they had been abandoned by their leaders," Hawking wrote in an op-ed for the Guardian. "It was, everyone seems to agree, the moment when the forgotten spoke, finding their voices to reject the advice and guidance of experts and the elite everywhere."

He added: "We face awesome environmental challenges: climate change, food production, overpopulation, the decimation of other species, epidemic disease, acidification of the oceans. Together, they are a reminder that we are at the most dangerous moment in the development of humanity...We can do this, I am an enormous optimist for my species; but it will require the elites, from London to Harvard, from Cambridge to Hollywood, to learn the lessons of the past year. To learn above all a measure of humility."

Hawking has expressed his reservations about Trump before. "He is a demagogue, who seems to appeal to the lowest common denominator," Hawking told ITV's "Good Morning Britain" program in May.

Hawking has also argued that immigration benefits the U.K. by encouraging the exchange of scientific ideas. Trump, meanwhile, has vowed to immediately deport 3 million undocumented immigrants and limit immigration from Arab nations.

A white Fiat van rammed into pedestrians outside enjoying a late afternoon stroll on Las Ramblas in Barcelona on Thursday killing at least 13 people and leaving hundreds injured. The Islamic State group claimed responsibility for the attack.